As is well known, a projector includes a light source, a light modulating device, and a projection lens. The projector modulates light emitted from the light source by the light modulating device and displays an image on a screen by projecting the modulated light onto the screen through the projection lens. While a typical projector of the related art includes, as a light source, a lamp such as a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp, projectors including a solid-state light source, such as a laser diode (LD) or a light emitting diode (LED), have recently been actively developed for reduction of power consumption, size, and weight.
One type of projector including a solid-state light source obtains red light, green light, and blue light necessary for color display by exciting a phosphor material with light emitted from the solid-state light source (e.g., blue laser light or ultraviolet laser light). Since such a projector can obtain three color lights (red light, green light, and blue light) necessary for color display by using only one solid-state light source, cost and size reduction is possible compared to a projector including a plurality of solid-state light sources.
The following PTL 1 discloses a technique that changes the light emitting and non-emitting period of a solid-state light source provided in an image forming apparatus so as to prevent scroll noise from being caused by pulse width modulation (PWM) of the solid-state light source. Here, the term “scroll noise” is a phenomenon in which band-shaped bright and dark portions extending in the lateral direction of the screen slowly move upward or downward on the screen. Further, the following PTL 2 discloses a technique that ensures a long life of a phosphor material provided in a projector by rotating the phosphor material to reduce damage due to light emitted from a solid-state light source.